1. Field of the Invention
The present disclosure relates to a LED backlight driving circuit technology, and more particularly to a LED backlight driving circuit for adjusting an output voltage and the liquid crystal device (LCD) with the same.
2. Discussion of the Related Art
With the technology revolution, backlight technology of LCDs are developed. Typical LCDs adopt cold cathode fluorescent lamps (CCFL) as the backlight. However, as the CCFL backlight is characterized by attributes including low color reduction ability, low lighting efficiency, high discharging voltage, bad discharging characteristics in low temperature, and also, the CCFL needs a long time to achieve a stable gray scale. As such, LED is a new developed backlight technology.
Generally, LED backlight is arranged opposite to liquid crystal panels in LCDs so as to provide light sources to the liquid crystal panels. The LED backlight includes at least one LED string having a plurality of LED serially connected. In the manufacturing process or assembling process of the LED backlight, the voltage applied to the LED string may be smaller than a default value due to inaccuracy.
FIG. 1 is a circuit diagram of a driving circuit of a conventional LED backlight of LCD. As shown in FIG. 1, the LED backlight driving circuit includes a boost circuit 110, at least one LED string 120, a reference voltage module 130, and a voltage control module 150. The boost circuit 110 is controlled by the voltage control module 150 to convert the input voltage to a needed output voltage so as to provide the output voltage to the LED string 120. When the driving voltage remains unchanged, if the voltage of the LED string 120 is larger than a normal range, the voltage drop of the LED string 120 is too large. The driving voltage may be smaller than the voltage of the LED string 120, which results in a LED string 120 malfunction, if the driving voltage has not been adjusted. On the other hand, the driving voltage may be larger than the voltage of the LED string 120 and the voltage drop of the LED string 120 is too small if the driving voltage has not been adjusted. Under the circumstance, the voltage of the negative end of the LED string 120 is too large, and the power consumption increases. It is obvious the driving circuit is not capable of adjusting the output voltage in accordance with the voltage drop of the LED string 120.